Map: 49th St. & Van Buren

While 97 million taxpayers have already filed their returns, there are, as always, those who have waited until the last possible minute to get their returns in the mail, and still others who will be filing Form 4868 to get a six-month extension.

While an extension gives you more time to file your returns, it does not give you more time to pay if you owe.

"The rules are that you have to pay 100 percent of your last year's liability or 90 percent of your current-year liability in order to not receive a penalty," Hockensmith explained.

If you owe but are not ready to file your paperwork, the extension -- Form 4868 -- is essential.

The penalty for a late payment with an extension is 0.5 percent of what you owe. Without an extension, that penalty jumps to 5 percent.

"The extension is very important to get in," Hockensmith said.

If you can't pay your tax in its entirety right now, you can file a Form 9465 to establish a payment plan if you owe less than $50,000. "That form allows you up to five years to pay the tax that you owe," Hockensmith said.

If you go that route, you need to know that the interest is 8 percent, compounded daily. That works out to 18.5 percent per year.

Still, tax experts say it's better to file for an extension and take your time rather than rush through the forms and risk making a potentially costly mistake.
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For those taxpayers who are old-school are rely on the U.S. Postal Service to get their returns to the IRS, the main Post Office on 49th and Van Buren streets will be open until 9:30 p.m.

"We do have a satellite drive-through station at the Phoenix Municipal station. That's going to be located on Van Buren and 56th Street," USPS spokeswoman Julie House said Monday morning.

If you go to that drive-through station, which will be open 5 p.m.-10 p.m., you must have the correct postage already on your envelopes. That station is for drop-offs only and will not be selling stamps.

Neither location will have tax forms.

It's also important to note that regular Post Office locations will be operating on their normal schedules. Check USPS.com for specific locations and hours